Desalination & Seawater RO (SWRO) Plants

Seawater reverse osmosis (SWRO) forces seawater (TDS 25,000–45,000 mg/L) through semi-permeable membranes at high pressure (55–70 bar) to separate freshwater from dissolved salts. The membranes reject ≥99.5% of dissolved salts, producing permeate with TDS of 100–500 mg/L. SWRO has largely replaced thermal desalination methods (MSF, MED) in new installations because of its lower specific energy consumption — 3–4 kWh/m³ with energy recovery devices, compared to 10–15 kWh/m³ for thermal.

SWRO (seawater RO) treats seawater at TDS 25,000–45,000 mg/L and operates at 55–70 bar with 50–60% recovery. BWRO (brackish-water RO) treats lower-salinity water at TDS 500–10,000 mg/L and operates at 15–25 bar with 75–85% recovery. The higher operating pressure and lower recovery of SWRO are driven by the higher osmotic pressure of seawater. BWRO uses standard spiral-wound elements; SWRO uses high-pressure elements designed for sustained high-bar operation with higher salt rejection.

SR Paryavaran Engineers delivers desalination plants from 1 m³/hr (24 CMD) to 50 m³/hr (1,200 CMD) per unit in containerised and skid-mounted formats. Higher capacities are delivered as multi-container or multi-skid assemblies. SRPEPL has delivered over 4,000 packaged RO and UF systems, including containerised SWRO and BWRO units.

Yes. SRPEPL manufactures high-pressure seawater RO membrane elements (SRP HP series) at its facilities in Panchkula, India, under its membrane manufacturing brand SRP Membranes. The SRP HP series is designed for operation at 55–70 bar with ≥99.5% salt rejection, suitable for seawater feeds up to 45,000 mg/L TDS. SRPEPL also manufactures brackish-water RO elements (SRP BW series) for BWRO applications up to 10,000 mg/L TDS. In-house membrane manufacturing means the membrane specification is controlled within the same engineering team that designs and builds the desalination system.

A modern SWRO plant with energy recovery devices (ERDs) consumes 3–4 kWh/m³ of product water. Without ERDs, SWRO energy consumption is 5–6 kWh/m³ — ERDs recover energy from the high-pressure reject stream and reduce power consumption by approximately 40%. SRPEPL includes ERDs as standard on all SWRO configurations. BWRO energy consumption is significantly lower at 0.8–1.5 kWh/m³ because of the lower operating pressure required.

Yes. Containerised and skid-mounted BWRO plants at capacities up to ~10 m³/hr are compatible with solar photovoltaic power, either standalone with battery storage or in hybrid configuration with diesel genset backup. SWRO's higher specific energy consumption (3–4 kWh/m³) makes solar-only operation more challenging at larger capacities, but solar-diesel hybrid is viable for containerised SWRO up to 5–10 m³/hr. SRPEPL has delivered 108 solar-powered packaged RO plants for community drinking water in Maharashtra and can integrate solar power supply into desalination configurations on request.

Seawater contains suspended solids, organic matter, algae and colloidal material that foul SWRO membranes if not removed. SRPEPL uses UF (ultrafiltration) pre-treatment as standard on all SWRO systems — UF produces a consistently low SDI (<3) feed regardless of seasonal variation. Conventional pre-treatment (media filtration) is acceptable for BWRO on clean groundwater sources. The choice of pre-treatment determines membrane fouling rate, CIP frequency and membrane life — undersized pre-treatment is the most common root cause of poor SWRO performance.

Brine from SWRO contains dissolved salts removed from the feed at approximately 1.5–2× the feed TDS. For coastal plants, brine is typically discharged through a diffuser outfall into the sea, subject to MoEF CRZ Notification 2019 and local coastal authority approvals. For inland BWRO plants, brine must be managed through evaporation ponds, solar evaporation, or further concentration via reject-recovery RO or ZLD extension. SRPEPL designs brine-management systems as an integral part of the desalination scope, not as an afterthought.

SRPEPL supplies desalination plants across India and to export markets through its international office in Sharjah, UAE. In India, applications include coastal and island drinking water, community BWRO for high-TDS and fluoride-affected groundwater, industrial make-up water for coastal plants, and defence installations. Export markets served include the GCC (UAE, Saudi Arabia, Oman, Kuwait, Qatar, Bahrain), Africa (Nigeria, Kenya, Egypt, Tanzania) and Southeast Asia (Vietnam, Bangladesh, Sri Lanka). Defence desalination units have been supplied to US Military installations through KBR.